Bleach compositions have long been used in a variety of detergent, personal care, pharmaceutical, textile and industrial applications. They serve to bleach and clean the surfaces into which they are brought into contact, and provide a disinfectant activity. Alkali metal hypohalite bleaches have long been used in household cleaning products and the textile and paper industries for the bleaching and cleaning of fabrics and wood fibers. They are also commonly used in cleaning products for disinfecting purposes. A typical alkali metal hypohalite is sodium hypochlorite. Peroxygen bleaches are less harsh than hypohalite bleaches and do not release objectionable gases or odors. This makes the use of such bleaches far more versatile, especially for personal care, oral care, and pharmaceutical compositions. Such bleaching agents, in the form of sodium percarbonate or sodium perborate, are commonly employed in powder or granular laundry detergent compositions and release active oxygen bleach upon exposure into an aqueous media.
Bleach compositions are often provided with increased viscosity for a wide variety of reasons, such as to enhance the aesthetics of a composition, improve ease of use, aid in suspension of other compositional ingredients, and to increase the residence time of the composition on application to vertical surfaces.
The use of polymeric rheology modifiers in these applications provides additional benefits in the unique rheology that they impart. These polymers tend to exhibit shear thinning rheological behavior. In other words, compositions thickened using polymeric rheology modifiers will, upon exposure to shear stress, show a decrease in their viscosity, which will allow easier delivery and application to and on their target substrate. Furthermore, upon removal of the shear stress, these compositions will rapidly recover to their initial viscosity. This property allows such compositions to be easily used with sprayer or trigger nozzle packaging despite their high initial or at rest viscosity.
Compositions containing polymeric rheology modifiers can exhibit a yield value which imparts vertical cling to non horizontal surfaces. The property of vertical cling enhances the contact time of the composition on its target substrate providing enhanced performance. This is especially valuable in compositions containing bleaches as enhanced bleaching and disinfecting will result. Further benefits of rheology modified compositions are noted in European Patent Publication (EP) 0606707 to Choy in the observation of decreased misting, reduced bleach odor, and a reduction in the amount of the composition that bounces back from a surface upon application. These attributes are of increased value for compositions containing bleaches by increasing the amount of product that is applied to the target substrate and reducing unintended and potentially harmful exposure of the composition to the person applying the composition.
Alkali metal hypohalite bleaches containing rheology modifiers are known. For example, U.S. Pat. No. 5,549,842 to Chang teaches the use of tertiary amine oxide surfactants to thicken hypohalite bleach containing compositions with 0.5 to 10.0% active chlorine levels. Also, U.S. Pat. No. 5,279,755 to Choy teaches the use of aluminum oxide thickeners to suspend calcium carbonate abrasive particles in the presence of a halogen bleach. However, many conventional polymeric rheology modifiers accelerate the degradation of hypohalite bleaches and thus are problematic for use in such compositions. Many of these polymers are themselves chemically unstable in the presence of a hypohalite bleach. Achieving a stable viscosity over the life of the composition has proven to be very difficult. To achieve stability, a variety of techniques have been employed. For example, Finley et al. in EP 0373864B1 and U.S. Pat. No. 5,348,682 teaches the use of a dual thickening system of an amine oxide surfactant and a polycarboxylate polymer to thicken chlorine bleach compositions with 0.4 to 1.2 available chlorine levels. U.S. Pat. No. 5,169,552 to Wise teaches the use of substituted benzoic acid structures in thickened liquid cleaning compositions with 0.2 to 2.5% active hypochlorite bleach and cross-linked polyacrylate polymer rheology modifiers. U.S. Pat. No. 5,529,711 and European Patent Publication 0649898 to Brodbeck et al. discloses the addition of alkali metals of benzoic acid as a hydrotrope to maintain viscosity and/or phase stability in the presence of certain anionic co-surfactants in thickened abrasive cleaning compositions. These compositions contain a dual surfactant and cross-linked polyacrylate polymer thickening system with 0.1 to 10.0% of a hypochlorite bleach. However, it was noted that none of the example compositions provided contained benzoic acid. Bendure et al. (EP 0523826) also discusses the addition of substituted benzoic acid structures to compositions containing cross-linked polyacrylate polymers and 0.2 to 4.0% hypochlorite bleach. The stated function of the additive is to increase the rate of flow of the composition from a container having an outlet opening of 8.45 mm in diameter.
Further, U.S. Pat. Nos. 5,185,096 and 5,225,096 and 5,229,027 disclose the use of iodine and iodate additives to improve the stability of cleaning compositions containing cross-linked polyacrylate polymers with 0.5 to 8.0% hypochlorite bleach. U.S. Pat. No. 5,427,707 to Drapier disclose the use of adipic or azelaic acid to improve the stability of cleaning compositions containing cross-lined polyacrylate polymers and 0.2 to 4.0% hypochlorite bleach. U.S. Pat. No. 5,503,768 to Tokuoka et al. teaches the use of aromatic compounds containing an oxygen, sulfur or nitrogen atom adjacent to the aromatic ring as halogen scavengers to suppress the release of halogen gas in acidic compositions if a halogen bleach is inadvertently added. But, Tokuoka is silent about improving the stability of a polymeric thickened compositions containing an halogen bleach. Further, while European Patent Publication 0606707 to Choy et al teaches the use of cross-linked polyacrylate polymers to thicken 0.1 to 10.0% hypochlorite compositions, per se, it does not show any stability data for the example compositions which are disclosed.
Aqueous peroxygen bleach compositions generally have not been utilized as much as alkali metal hypohalites bleaches due to the greater instability of peroxygen bleaches in aqueous compositions. The greater instability is especially relevant and frequently noted for alkaline pH compositions. Alkaline pH's are commonly preferred for cleaning, disinfecting, and hair dyeing applications. Considerable effort has been expended in the search for stabile aqueous peroxygen bleach compositions. For example, U.S. Pat. No. 4,046,705 to Yagi et al. teaches the incorporation of a chelating compound which is an unsaturated 5 or 6 member heterocyclic ring compound to inorganic peroxygen bleaches for powder laundry detergents to improve the stability in such compositions. U.S. Pat. Nos. 4,839,156 and 4,788,052 to Ng et al. discloses aqueous gelled hydrogen peroxide dental compositions where the gelling agent is a poly-oxyethylene poly-oxypropylene block copolymer surfactant. Additionally, Ng controls the pH of such compositions to limit them to 4.5 to 6.0. U.S. Pat. No. 4,839,157 to Ng et al. discloses aqueous hydrogen peroxide dental compositions where the gelling agent is fumed silica and the pH is 3 to 6. U.S. Pat. No. 4,696,757 to Blank et al. discloses aqueous gelled hydrogen peroxide compositions where the gelling agent is a poly-oxyethylene poly-oxypropylene block copolymer surfactant with glycerin, and the pH is limited to 6.
U.S. Pat. No. 4,238,192 to Kandathil discloses hydrogen peroxide compositions useful for household products having a pH of 1.8 to 5.5, but does not teach the use of gelling agents or thickened products. U.S. Pat. No. 4,497,725 to Smith et al. discloses aqueous alkaline peroxide formulations which use substituted amino compounds and phosphonate chelators for improved stability, but without using gelling agents.
U.S. Pat. No. 5,393,305 to Cohen et al. discloses a two part hair dye system where the developer phase contains a polymeric thickener and hydrogen peroxide. The polymeric thickener is limited to a copolymer that is insoluble in the developer phase, which has a pH range 2 to 6. The polymer becomes soluble and thickens upon reaction with the alkaline dye phase upon application. U.S. Pat. No. 5,376,146 to Casperson et al. also teaches the use of polymeric thickeners to thicken hydrogen peroxide in the developer phase of a two part hair dye application, where the polymeric thickener is limited to copolymers that are insoluble in the developer phase and the pH of the developer phase is 2 to 6. Casperson teaches against the use of cross-linked polyacrylate polymers or carbomers as they are soluble in the developer phase and are not stable.
Other teachings of peroxide systems, which are not suggested for thickened systems include, U.S. Pat. No. 5,419,847 to Showell et al. which teaches aqueous compositions containing hydrogen peroxide and bleach activators, where the pH is 3.5 to 4.5 and enhanced stability is provided by the addition of carboxylate, polyphosphate and phosphonate chelators. U.S. Pat. No. 5,264,143 to Boutique discloses stabilized compositions containing a water soluble peroxygen bleach. Enhanced stability is provided by the addition of diphosphonate compounds to chelate residual transition metals. The pH of such compositions are greater than 8.5. U.S. Pat. No. 4,900,468 to Mitchell et al. discloses aqueous compositions containing hydrogen peroxide, surfactant, fluorescent whiteners and dyes. The compositions are stabilized with the addition of heavy metal chelators and free radical scavengers. The preferred free radical scavengers are butylated hydroxy toluene (BHT) and mono-ter-butyl hydroquinone (MTBHQ). The pH of such compositions are most preferably from 2-4. U.S. Pat. No. 5,180,514 to Farr et al. discloses aqueous compositions containing hydrogen peroxide, surfactant, fluorescent whiteners and dyes. The compositions are stabilized with the addition of heavy metal chelators and free radical scavengers. The preferred free radical scavengers are amine free radical scavengers. The pH of such compositions are most preferably from 2-4.
Literature from Solvay Interox, which is a supplier of peroxide compounds, entitled "Thickened Hydrogen Peroxide" and "Hydrogen Peroxide Compatible Ingredients", teaches gelling aqueous compositions containing hydrogen peroxide with cross-linked polyacrylate polymers, but this teaching is at an acidic pH range and does not suggest the use of stabilizing agents.
As is seen from the above discussion, in making gelled aqueous compositions containing bleaches and rheology modifying polymers, the type and level of the bleach, the compositional pH, and the particular polymer are all factors to be carefully considered in order to obtain a stable composition. Thus, there is need for thickened bleach compositions having greater formulation flexibility and stability across a variety of variables.